Tag Archives: A New Control Strategy for Active and Reactive Power Control of Three-Level VSC Based HVDC System

This paper presents a new control strategy for real and reactive power control of three-level multipulse voltage source converter based High Voltage DC (HVDC) transmission system operating at Fundamental Frequency Switching (FFS). A three-level voltage source converter replaces the conventional two-level VSC and it is designed for the real and reactive power control is all four quadrants operation. A new control method is developed for achieving the reactive power control by varying the pulse width and by keeping the dc link voltage constant. The steady state and dynamic performances of HVDC system interconnecting two different frequencies network are demonstrated for active and reactive powers control. Total numbers of transformers used in the system are reduced in comparison to two level VSCs. The performance of the HVDC system is also improved in terms of reduced harmonics level even at fundamental frequency switching.

Fig. 2 Control scheme of three-level VSC based HVDC system using dynamic dead angle (β) Control

EXPECTED SIMULATION RESULTS

Fig. 3 Performance of rectifier station during simultaneous real and reactive power control of three-level 24-pulse VSC based HVDC system

Fig. 4 Performance of inverter station during simultaneous real and reactive power control of three-level 24-pulse VSC based HVDC system

Fig. 5 Variation of angles (δ) and (β) values of three-level 24-pulse VSC based HVDC system during simultaneous real and reactive power control

CONCLUSION

A new control method for three-level 24-pulse voltage source converter configuration has been designed for HVDC system. The performance of this 24-pulse VSC based HVDC system using the control method has been demonstrated in active power control in bidirectional, independent control of the reactive power and power quality improvement. A new dynamic dead angle (β) control has been introduced for three-level voltage source converter operating at fundamental frequency switching. In this control the HVDC system operation is successfully demonstrated and also an analysis of (β) value for various reactive power requirement and harmonic performance has been carried out in detail. Therefore, the selection of converter operation region is more flexible according to the requirement of the reactive power and power quality.